The companies involved in these mergers say they will improve coordination of care for consumers, but critics say consumers could be left with far fewer choices and potentially higher costs.

"This type of consolidation in a market already dominated by a few, powerful players presents the very real possibility of reduced competition that harms consumer choice and quality," George Slover, senior policy counsel for the advocacy group Consumers Union, said in a statement, The Times reported.

Trump to Sign Bills Lifting Drug Price 'Gag Orders' on Pharmacists

Two bills that allow U.S. pharmacists to disclose drug prices to customers to help them save money are expected to be signed Wednesday by President Donald Trump.

Previously, pharmacists could not tell consumers if the cash price for a prescription was less than what they would pay using their insurance plan, NBC News reported.

That was due to "gag order" clauses in contracts between pharmacies and insurance companies or pharmacy benefit managers.

The two bills were passed by Congress last month. One bill is for Medicare and Medicare Advantage beneficiaries and the other for commercial-based and individual policies, NBC News reported.

Consumers with Medicare Part D drug insurance overpaid for prescriptions by $135 million in 2013, according to a study published in JAMA earlier this year.

For nearly one quarter of drugs bought that year, copayments in those plans were higher than the cash price. The study also found that for 12 of the 20 most commonly prescribed drugs, patients overpaid by more than 33 percent, NBC News reported.

Eliminating pharmacist gag orders won't give consumers much relief from high drug prices, according to some critics.

"As a country, we're spending about $450 billion on prescription drugs annually," Steven Knievel, who works on drug price issues for Public Citizen, a consumer advocacy group, told NBC News.

The slight savings gained by paying the cash price "is far short of what needs to happen to actually deliver the relief people need," he said.